Laterally insertable artificial vertebral disk replacement implant with translating pivot point

ABSTRACT

An implant that can be placed between two vertebrae using a lateral insertion method is described. The implant is characterized by having a first end plate and a second end plate with a hemi-cylindrical spacer extending from the second end plate. The hemi-cylindrical spacer fits within a socket on the first end plate and allows for pivotal or rotational motion and also for twisting motion.

CLAIM OF PRIORITY

This application claims priority under 35 USC 119 to U.S. Patent Application No. 60/526,724, filed on Dec. 2, 2003 and entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND LATERAL IMPLANT METHOD,” which is hereby incorporated by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Provisional Application No. 60/422,039, filed Oct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND METHOD,” U.S. patent application Ser. No. 10/684,668, filed Oct. 14, 2003, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH CROSSBAR SPACER AND METHOD,” U.S. patent application Ser. No. 10/684,669, filed Oct. 14, 2003, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND METHOD,” U.S. Provisional Application No. 60/422,011, filed Oct. 29, 2002, entitled “TOOLS FOR IMPLANTING AN ARTIFICIAL VERTEBRAL DISK AND METHOD,” U.S. patent application Ser. No. 10/685,134, filed Oct. 14, 2003, entitled “TOOLS FOR IMPLANTING AN ARTIFICIAL VERTEBRAL DISK AND METHOD,” U.S. Provisional Application No. 60/422,022, filed Oct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A SPACER AND METHOD,” U.S. Provisional Application No. 60/422,021, filed Oct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH CROSSBAR SPACER AND METHOD,” U.S. patent application Ser. No. 10/685,011, filed Oct. 14, 2003, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH SPACER AND METHOD,” U.S. patent application Ser. No. ______, filed ______, entitled “METHOD OF LATERALLY INSERTING AN ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT,” (KLYCD-05007US6), U.S. patent application Ser. No. ______, filed ______, entitled “LATERALLY INSERTABLE ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A CROSSBAR SPACER,” (KLYCD-05008US6), U.S. patent application Ser. No. ______, filed ______, entitled “METHOD OF LATERALLY INSERTING AN ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A CROSSBAR SPACER,” (KLYCD-05008US7), U.S. patent application Ser. No. ______, filed ______, entitled “LATERALLY INSERTABLE ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A SPACER,” (KLYCD-05010US4), U.S. patent application Ser. No. ______, filed ______, entitled “METHOD OF LATERALLY INSERTING AN ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A SPACER,” (KLYCD-05010US5), all of which are incorporated herein by reference.

FIELD OF ART

This field of art of this disclosure is directed to an artificial vertebral disk replacement and method.

BACKGROUND

The spinal column is a biomechanical structure composed primarily of ligaments, muscles, vertebrae and intervertebral disks. The biomechanical functions of the spine include: (1) support of the body, which involves the transfer of the weight and the bending movements of the head, trunk and arms to the pelvis and legs, (2) complex physiological motion between these parts, and (3) protection of the spinal cord and nerve roots.

As the present society ages, it is anticipated that there will be an increase in adverse spinal conditions which are characteristic of aging. For example, with aging comes an increase in spinal stenosis (including, but not limited to, central canal and lateral stenosis), and facet joint degeneration. Spinal stenosis typically results from the thickening of the bones that make up the spinal column and is characterized by a reduction in the available space for the passage of blood vessels and nerves. Facet joint degeneration results from the constant load borne by the facet joints, and the eventual wear that results. Pain associated with both conditions can be relieved by medication and/or surgery.

In addition, to spinal stenosis, and facet joint degeneration, the incidence of damage to the intervertebral disks is also common. The primary purpose of the intervertebral disk is to act as a shock absorber. The disk is constructed of an inner gel-like structure, the nucleus pulposus (the nucleus), and an outer rigid structure comprised of collagen fibers, the annulus fibrosus (the annulus). At birth, the disk is 80% water, and then gradually diminishes with time, becoming stiff. With age, disks may degenerate, and bulge, thin, herniate, or ossify. Additionally, damage to disks may occur as a result disease, trauma or injury to the spine.

The damage to disks may call for a range of restorative procedures. If the damage is not extensive, repair may be indicated, while extensive damage may indicate full replacement. Regarding the evolution of restoration of damage to intervertebral disks, rigid fixation procedures resulting in fusion are still the most commonly performed surgical intervention. However, trends suggest a move away from such procedures. Currently, areas evolving to address the shortcomings of fusion for remediation of disk damage include technologies and procedures that preserve or repair the annulus, that replace or repair the nucleus, and that advance implants for total disk replacement. The trend away from fusion is driven both by issues concerning the quality of life for those suffering from damaged intervertebral disks, as well as responsible health care management. These issues drive the desire for procedures that are minimally invasive, can be tolerated by patients of all ages, especially seniors, and can be performed preferably on an out patient basis.

Most recently, there has been an increased interest in total disk replacement technology. A number of artificial disks are beginning to appear in the medical device marketplace. These artificial disks vary greatly in shape, design and functionality. With these devices go tools and methods for insertion between vertebrae thereof.

Accordingly, there is a need in the art for innovation in technologies and methods that advance the art in the area of minimally invasive intervertebral disk replacement. This not only enhances the quality of life for those suffering from the condition, but is responsive to the current needs of health care management.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a posterior view of an embodiment of the assembled implant of the invention. FIG. 1B is a cross-section of the device shown in FIG. 1A. FIG. 1C is a posterior view of two bottom plates of the implant of the embodiment of the invention. FIGS. 1D and 1E are posterior views of the embodiment of the implant of the invention shown in FIG. 1A illustrating the operation of the device in bending to the left and bending to the right, respectively.

FIG. 2A is a side view of the implant of FIG. 1A showing the implant in flexion. FIG. 2B is a side view of the implant showing the implant in extension. FIG. 2C is a partial cross-sectional view of a side view of the implant of an embodiment of the invention. FIG. 2D is a partial cross-sectional view of an alternative embodiment of the implant of the invention having a protuberance adjacent the socket.

FIG. 3A is a top view of a portion of an embodiment of the assembled implant of the invention. FIG. 3B is a top view of an embodiment of the implant of the invention showing a rotation to the right. FIG. 3C is a top view of an embodiment of the implant of the invention showing a rotation to the left.

FIG. 4A and FIG. 4B show perspective views of the first and second inner surfaces of the first end plate and the second end plate of an embodiment of implant 100.

FIG. 5A is a posterior view of the embodiment of the implant of the invention after being implanted between two vertebral bodies. FIG. 5B is a side view of the embodiment of the implant of the invention after being implanted between two vertebral bodies.

FIG. 6A is a rear view of an alternate embodiment of the invention having two plates. FIG. 6B and FIG. 6C show perspective views of the first and second inner surfaces of the first end plate and the second end plate of an alternative embodiment of implant 600. FIG. 6D is a cross sectional view of the embodiment shown in FIG. 6A.

FIG. 7A is a top view of an embodiment of a cutting tool of the invention used to prepare the vertebral bodies for the implant. FIG. 7B is a side view of the embodiment of the cutting tool of the invention from the distal end. FIG. 7C is a distal end view of an embodiment of the cutting tool of the invention.

FIG. 8A is a side view of an embodiment of the implant lateral insertion tool of the invention. FIG. 8B is a top view of the embodiment of the implant lateral insertion tool of the invention. FIG. 8C is a distal end view of the embodiment of the implant lateral insertion tool of the invention. FIG. 8D is a top view of an embodiment of the implant lateral insertion tool holding an embodiment of the implant.

FIG. 9 is a block diagram illustrating the steps of a method for inserting the implant between vertebral bodies.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use what is disclosed. Various modifications to the embodiments described will be readily apparent to those skilled in the art, and the principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of what is disclosed and defined by the appended claims. Thus, what is disclosed is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. To the extent necessary to achieve a complete understanding of what is disclosed herein, the specification and drawings of all patents and patent applications cited in this application are incorporated herein by reference.

FIG. 1A shows an embodiment of the implant 100 having a four-piece configuration. The designations, “A” for anterior, “P” for posterior, “RL” for right lateral, and “LL” for left lateral are given in the drawings for spatial orientation. These designations give the relationship of all faces of embodiments of the disclosed intervertebral implant from the superior perspective; i.e. looking down the axis of the spine. The implant 100 has a pair 131 of first end plates, or upper end plates 110 that are configured to mate with a first vertebra. The upper end plate 110 of implant 100 has a first outer surface 112 from which a first keel 114 extends with a first set of teeth 115. Additionally, the implant 100 has a pair 133 of second end plates, or lower end plates 120 that are configured to mate with a second vertebra. The lower end plate 120 has a second outer surface 122 from which a keel 124 extends with a second set of teeth 125. A pair of pivoting or articulating elements or spacers 130 that are part of the pair 133 of lower end plates 120 acts as an articulating element, or spacer between the first end plate 110 and the second end plate 120 and facilitates pivotal or rotational and also twisting movement of the first end plate 110 and the second end plate 120, relative to each other. In the embodiments described, the pair of articulating elements, or spacers 130 is curved or convex, as will be discussed in more detail below.

Several configurations of implant 100 are contemplated. For instance, FIG. 6A illustrates a posterior view of an alternate embodiment of the implant shown in FIG. 1A. The implant 600 of FIG. 6A is in the form of a two-piece implant 600 having a first end plate 610 and a second end plate 620. The first end plate, or upper end plate 610 is configured to mate with a first vertebra, and a second end plate, or lower end plate 620 is configured to mate with a second vertebra. The first inner surface 616 of the upper end plate 610 has a socket or first cavity 636 formed therein. A pivoting or articulation element, or spacer 630 is formed on second end plate 620. The spacer 630 at least partially engages the first socket 636, and facilitates pivotal or rotational and also twisting movement of the first end plate 610 and the second end plate 620, relative to each other. The spacer 630 and corresponding socket 636 are dimensioned so that they are hemi-cylindrical (FIG. 6D), while in another embodiment shown in FIG. 6B and FIG. 6C, the articulating element, or spacer 630 and corresponding socket 636 are hemispherical.

The upper end plate 610 of implant 600 has a first outer surface 612 from which a first keel 614 extends with a first set of teeth 615. In one embodiment, when implant 600 is inserted between vertebrae, the first keel 614 extends longitudinally across the first outer surface 612, about perpendicular to the sagittal plane of the spine. In another embodiment, the first keel 614 extends longitudinally only partially across the first outer surface 612, about perpendicular to the sagittal plane of the spine. The teeth 615 in the two embodiments with complete or partial extension of the keel 614 across the first outer surface 612 of the upper end plate 610 point towards the left lateral face of implant 600 when the embodiment is meant to be put into a slot in a vertebral body from the left lateral approach to the spine. This orientation is shown in the figures, and is particularly evident where the keel 614 is fully displayed, as in FIG. 1A and FIG. 6A, for example. Alternatively, the teeth 615 point towards the right lateral face of implant 600 when the embodiments are meant to be put into a slot in a vertebral body from the right lateral approach to the spine.

The first outer surface 612 abuts the vertebral body when the implant 600 is implanted. The first keel 614 extends into the vertebral body to anchor implant 600 into position, and is perpendicular to the median sagittal plane of the spine, in which extension and flexion occur. The first keel 614 in this orientation offers substantial stability during extension and flexion for the implant 600 inserted between the vertebrae of a patient. Additionally, the first keel 614 in this embodiment is preferably aligned with and supports the articulation of implant 600. The first inner surface 616 with socket 636 at least partially engages the spacer 630 of the implant and opposes the second end plate 620. The first inner surface 616 can form a planar surface that is parallel to the first outer surface 612, or can form a planar surface that is not parallel to the first outer surface 612.

The lower end plate 620 has a second outer surface 622 from which a keel 624 extends with a second set of teeth 625. In one embodiment, when implant 600 is inserted between vertebrae, the second keel 624 is about perpendicular to the sagittal plane of the spine. As described above for the first upper end plate 610, in one embodiment, the second keel 624 extends longitudinally across the second outer surface 622, while in another embodiment, the second keel 624 extends longitudinally partially across the second outer surface 622. The teeth 625 in the two embodiments with complete or partial extension of the second keel 624 across the second outer surface 622 of the lower end plate 620 point towards the left lateral face of implant 600 when the embodiment is meant to be put into a slot in a vertebral body from the left lateral approach to the spine. This orientation is shown in the figures, and is particularly evident where the second keel 624 is fully displayed, as in FIG. 1A and FIG. 6A, for example. Alternatively, the teeth 625 point towards the right lateral face of implant 600 when the embodiments are meant to be put into a slot in a vertebral body from the right lateral approach to the spine.

The second outer surface 622 abuts the vertebral body when the implant 600 is implanted. The second keel 624 extends into the vertebral body to anchor implant 600 into position, and is perpendicular to the median sagittal plane of the spine, in which extension and flexion occur. The second keel 624 in this orientation offers substantial stability during extension and flexion for the implant 600 inserted between the vertebrae of a patient. Additionally, the second keel 624 in this embodiment is aligned with and supports the articulation of implant 600. The second end plate 620 with second inner surface 626 having the spacer 630 opposes the first end plate 610 with first inner surface 616 having socket 636. The spacer 630 of second inner surface 626 at least partially engages socket 636 of first upper surface. The second inner surface 626 can form a planar surface that is parallel to the second outer surface 622, or can form a planar surface that is not parallel to the second outer surface 622.

The first inner surface 616 of the first end plate 610 can be parallel to the second inner surface 626 of the second end plate 620 when the implant 600 is assembled and is in a neutral position (i.e., the position where the first end plate 610 has not rotated relative to the second end plate 620). Alternatively, the first inner surface 616 of the first end plate 610 can be non-parallel to the planar surface of the second inner surface 626 of the second end plate 620 when the implant 600 is assembled and in a neutral position. This non-parallel orientation of the first end plate 610 and the second end plate 620 allows the plates to pivot to a greater degree with respect to each other. Additionally, factors such as the height and position of the spacer 630, and the, can also be adjusted in order to increase the degree that the first end plate 610 and the second end plate 620 can pivot relative to each other. Other factors that effect the degree of movement of the first end plates 110 or 610 relative to the second end plates 120 or 620 for implant 100 or implant 600 will discussed below.

When implant 600 is inserted between vertebrae the planar surfaces corresponding to the first and second outer surfaces 612, 622 and the first and second inner surfaces 616, 626 of the first and second end plates 610, 620 lie within, or substantially within, the axial plane of the body. Similarly, the first and second keels 614, 624 are aligned in the axial plane, or perpendicular to the sagittal plane of the vertebrae. The first and second keels 614,624 extend into the vertebral bodies to anchor implant 600 into position, and are perpendicular to the median sagittal plane of the spine, in which extension and flexion occur. The first and second keels 614,624 in this orientation offer substantial stability during extension and flexion for implant 600 inserted between the vertebrae of a patient. Additionally, the first and second keels 614,624 in this embodiment are aligned with and support the axis of articulation of implant 600 defined by an RL to LL orientation.

The lateral orientation of the keels allow the implants to be inserted into the spine using a lateral approach as opposed to an anterior or posterior approach. The lateral approach is advantageous, because the spinal nerves in the spinal cavity are minimally undisturbed when the implants are inserted laterally into the spine. In comparison to a posterior insertion approach in which the spinal nerves can be substantially disturbed, the spinal nerves are bypassed and relatively undisturbed when the implant is inserted laterally between the vertebral bodies from the side of the spine. Although an anterior insertion approach has its benefits, the lateral insertion approach can allow the present implant and associated implantation tools, to be inserted into the spine with less disturbance of the patient's internal organs. This can translate into less time and risk associated with preparing the spine for insertion as well as inserting the implant itself into the spine. Further, the laterally oriented keels offer substantial stability to the vertebral bodies during extension, flexion and lateral bending of the spine.

In the embodiment shown in FIG. 1A and FIG. 6A, the first and second keels 114,124 and 614,624 include ports 148,152 and 648,652, respectively, that facilitate bone ingrowth. For example, bone from the vertebral bodies can grow thorough the ports 148,152 and 648,652, and aid in securing the first and second keels 114,124 and 614,624, and thereby for securing implants 100 and 600 once inserted between vertebral bodies. In addition, surfaces defined by the first and second keels 114,124 and 614,624 and the first and second outer surfaces 112,122 and 612, 622 of implants 100 and 600 can be roughened in order to promote bone ingrowth into these defined surfaces of implants 100 and 600. In other embodiments the ports 148,152 and 648,652, the first and second keels 114,124 and 614,624, and the first and second outer surfaces 112,122 and 612, 622 of implant 600 can be coated with materials that promote bone growth such as for example bone morphogenic protein, BMP, or structural materials such as hyaluronic acid, HA, or other substance which promotes growth of bone relative to and into the keels 614,624, keel ports 648,652, and other external surfaces of the implant 600.

Further, a combination of the two embodiments shown in FIG. 1A and FIG. 6A can be used to create a three-piece implant as will also be appreciated by those of ordinary skill in the art. For example, the first end plate 610 of FIG. 6A with its socket 636 from a two-piece embodiment can be combined with two second end plates 120 of FIG. 1A from a four-piece embodiment to form an implant. Similarly, the second end plate 620 with spacer 630 of a two piece embodiment, such as FIG. 6A, can be combined with two first end plates 110 from a four-piece design, such as FIG. 1A, to achieve an implant. The features described herein for an interspinous implant for lateral insertion between adjacent vertebrae are applicable to two-, three-, or four-piece embodiments. None of these configurations depart from the scope of the invention.

FIG. 1B depicts the pair 131 of first or upper end plates 110 and the pair 133 of second or lower end plates 120 in cross-section. Each upper and lower end plate 110,120 has a keel 114,124 with a set of teeth 115,125. As for implant 600, different embodiments of implant 100 may have complete or partial extension of the first and second keels 114,124 across the first and second outer surfaces 112,122 of the upper and lower end plates 110,120. The teeth 115,125 point towards the left lateral face of implant 100 when the embodiment is meant to be put into a slot in a vertebral body from the left lateral approach to the spine, and alternatively, the teeth 115,125 point towards the right lateral face of implant 100 when the embodiments are meant to be put into a slot in a vertebral body from the right lateral approach to the spine.

In FIG. 1B, the socket 136 formed in the first inner surface 116 of first end plate 110 has a first elongated sidewall 150, a corresponding second elongated sidewall 152 (shown in FIG. 3B), an end wall 154, and an open end 156. The open ends 156 of each of the first end plates 110 are oriented so that the open ends 156 face each other. Each of the first and second end plates 110, 120 has a first end 138, 141 and a second end 139, 143. The ends 139 of the first end plate 110 face each other, as do the ends 143 of the second end plate 120. The lower plates 120 each have an articulating element, or spacer 130, which is convex and hemi-cylindrical, that engage the socket 136. The concave hemi-cylindrical inner surface 135 of the socket 136 is sloped to allow the pair 131 of first or upper end plates 110 to easily slide, or rock, side-to-side on the articulating element, or spacer 130 and slide, or ride, forward and backward with enough looseness of fit to allow for some twisting in order to emulate the motion of the vertebral bone and intervertebral disk tissue. This arrangement, thus, has a sliding or translating pivot point. It is evident from FIG. 1B that the first and second keels 114,124 are aligned with and support the axis of articulation of the upper end plate 110 about the spacer 130 for this embodiment. This axis of articulation is longitudinally oriented with respect to the vertebrae, or about perpendicular to the sagittal plane of the spine. The alignment of the first and second keels 114,124 with the axis of articulation offers substantial stability during flexion and extension when implant 100 is inserted between the vertebrae of a patient.

As shown in FIG. 1C, the articulating element, or spacer 130 has four sides: a first elongated sidewall 140, a second elongated sidewall 142, a third end wall 143, and a fourth end wall 146. The third end wall 144 is flush with the end 143 of the lower end plate 120 of the implant. The third end wall 144 has a profile height 160 and the fourth end wall 146 has a profile height 162. Comparing the profile heights 160, 162 to each other at the same point on the second inner surface 126 of the second end plate 120, the overall profile height of the third end wall 144 is greater than the fourth end wall 146 (i.e., 160>162). Thus, it is evident that the upper surface 135 of socket 136 slopes downwardly from the end wall 144 to the end wall 146. Together spacers 130 comprise an articulating element that has a high surface where the third end walls 144 abut each other and slope to a lower surface adjacent to fourth end walls 146.

In FIG. 1C, the edges of the articulating element or spacer 130 are eased or rounded to allow for further range of motion of the pair 131 of upper end plates 110 relative to the pair 133 of lower end plates 120. As will be appreciated by those of skill in the art, the overall height of the third end wall 144 and the fourth end wall 146 can be equivalent while still having an effective third end wall height 160 that is greater than the effective fourth end wall height 162 due to the overall slope of the second inner surface 126. Alternatively, the overall height of the third end wall 144 and the fourth end wall 146, can be different with the third end wall 144 having a height greater than the fourth end wall 146, thus eliminating the need for the second inner surface 126 to have a slope or further increasing the net difference between the height of the third end wall and the forth end wall. Further, although the spacer 130 is depicted such that the third end wall 144 is flush with the second end 143, those of skill in the art will appreciate that the spacer 130 could also be configured such that the third end wall 144 is recessed relative to the end 143 of the second end plate. In such a configuration, the third end wall 144 and the end 143 would not be flush.

FIGS. 1D and 1E illustrate posterior views of the implant 100 showing the clearance for left and right lateral bending. Typically, left and right lateral bending ranges from 3-5°. As evident from these figures, the length of the spacer 130 can be less than the length of the socket 136. As shown, the open ends 156 of the sockets facilitate movement of the articulating elements, or spacers 130 within the socket 136 to accommodate side-bending movement.

FIG. 2A and FIG. 2B are views of the intervertebral implant 100, which depict the motion of the first end plate 110 relative to the second end plate 120. In FIG. 2A and FIG. 2B, a side view of implant 100 is depicted, showing first end plate 110 with socket 136 and the second end plate 120 with the articulating element or spacer 130. As is apparent from the figures, the sloping of the first inner surface 116 of the first end plate 110 facilitates rotation of the spacer and socket in an anterior A direction and a posterior P direction. As depicted, the first inner surface 116 slopes from a high point at about where the socket is located to low points at the ends 111 and 113 of the upper end plate 110. As shown in FIG. 2A, the implant 100 is positioned to achieve flexion (i.e., forward bending) in a range up to about 15°, but more preferably 10°, while in FIG. 2B, the implant 100 is positioned to achieve extension (i.e., backward bending) in a preferable range of up to about 5°.

FIG. 2C and FIG. 2D show cross sections of implant 100 through the sagittal plane of the vertebrae. FIG. 2C is a cross-section of the side view of the intervertebral implant 100 showing the mating of the spacer 130 to the socket 136. FIG. 2D illustrates an alternate embodiment of the first end plate 110 wherein the socket 136 has ridges 268, 269 forming a protuberance that extends into the channel 264, 265 respectively on the second end plate 120. As will be appreciated by those of skill in the art, the protuberances 268, 269 can extend partially into the channel, such as the configuration shown, or can have a channel conforming shape such that when the spacer and socket are moved to achieve flexion 272 or extension 274 the protuberance or ridge 268, 269 extends into the channels 264, 265. This embodiment allows the first inner surface 116 and second inner surface 126 of the first end plate 110 and the second end plate 120 to be flat and non-sloping as shown while still allowing for the implant to emulate forward and backward bending and allow for the blocking of the motion of the socket relative to the spacer. In this embodiment, it is noted that the first and second keels 114,124 are aligned with and support the articulation of first end plate 110 about the spacer 130 for this embodiment, and where the articulation is about perpendicular to the sagittal plane of the spine.

Turning now to FIG. 3A, a top view of one-half of the intervertebral implant 100 is shown. Each of the top first end plate 110 and the bottom second end plate 120 have a bores 376 for receiving pins of an implant tool. The first keel 114 on the first end plate 110 is positioned so that it is aligned in the same plane with the second keel 124 on the second end plate 120. Additionally, the length of spacer 130 from the third end wall 144 to the fourth end wall 146 is shorter than the length of the socket 136 from the end wall 154 to the open end 156, so that the fit of the spacer with the socket is somewhat loose. The loose fit of the spacer 130 in the socket 136 allows the first end plate 110 to be able to twist somewhat relative to the second plate 120. This twisting action would generally be about an axis that is perpendicular to the first and second inner surfaces 116,126 of the first and second end plates 110,120, respectively. Thus, implant 100 of this embodiment allows the spine to have movement in three orthogonal degrees of freedom, namely (1) forward and backward bending movement, (2) lateral side-to-side bending, and (3) twisting movement. FIGS. 3B and 3C show the relative rotation of the first or upper end plate 110 to the second or lower end plate 120 to achieve rotation about a central axis 378. This rotation results in about a 3°-6° rotation about the axis (i.e., 3° of torso twisting in each direction).

FIG. 4A and FIG. 4B show views of the first and second end plates, 110,120. FIG. 4A shows a perspective view of a second end plate 120 of the intervertebral implant 100. The second inner surface 126 of the second end plate 120 is shown with a hemi-cylindrical spacer 130 formed therefrom, and channels or grooves 264, 265 extending about the spacer 130. As illustrated in FIG. 4A, the channels 264, 265 are formed on two sides of the spacer 130. However, as will be appreciated by those of skill in the art, the channels 264, 265 can alternatively surround the spacer 130. The channels allow the sides of the spacer 130 to be made more perpendicular so as to create a greater blocking wall thus preventing the socket of the upper plate 100 from moving too much anteriorly or posteriorly relative to the lower plate 120. FIG. 4B shows a perspective view of the first end plate 110, with a first inner surface 116 that opposes the second inner surface 126. The first inner surface 116 has a hemi-cylindrical socket 136 formed therein. The socket 136 of FIG. 4B is configured to mate with the spacer 130 of FIG. 4A.

FIG. 4 c and FIG. 4 d show views of the first and second end plates, 110, 120 for an alternative embodiment of implant 100. FIG. 4 c shows a perspective view of an embodiment of the second inner surface 126 of the second or lower end plate 120 of implant 100. The second inner surface 126 of the lower end plate 120 has a hemispherical spacer 130 formed therefrom. FIG. 4 d shows a perspective view of an embodiment of the first inner surface 116 of the first or upper end plate 110 of implant 100, which opposes the second inner surface 126. The first inner surface 116 of the upper end plate 110 has a socket or cavity 136 formed therein. In the embodiment of FIG. 4 d, the socket 136 has a concave hemispherical surface. The socket 136 allows the first end plate 110 to pivot or rotate on spacer 130.

In the embodiments shown in FIG. 4A and FIG. 4B, it is noted that the first and second keels 114,124 are aligned with and support the articulation of the first end plate 110 about the spacer 130, relative to the second end plate 120. The first and second keels 114,124 in this orientation offer substantial stability during extension and flexion for implant 100 inserted between the vertebrae of a patient. Additionally, the first and second keels 114,124 in these embodiments are aligned with and support the lateral axis of articulation of implant 100, which is perpendicular to the sagittal plane of the spine. Additionally, as evidenced from the perspective views of FIG. 4A and FIG. 4B, the perimeter shape of the upper and lower end plates 110,120 can be configured to correspond to the perimeter shape of a vertebral disk. As will be appreciated by those of ordinary skill in the art, the perimeter shape of the upper end plate 110 and the lower end plate 120 can be the same.

FIG. 5A and FIG. 5B show the implant after insertion between the vertebrae of a patient. FIG. 5A illustrates a posterior view of the implant shown in FIG. 1A implanted between vertebral bodies in a spine. FIG. 5A illustrates the spinal column 500 and the cauda equina 504 (a collection of lumbar and sacral nerve roots that fill the caudal end of the spinal cord) with individual nerves 506 exiting the cord between lumbar vertebrae. The implant 100 is positioned between two vertebral bodies 520, 521 such that the first and second keels 114, 124 lie in a plane parallel to coronal or frontal plane of the body, or perpendicular to the sagittal plane of the vertebrae. FIG. 5B illustrates a side view of the implant inserted between vertebral bodies 520, 521, for embodiments of the implant as that shown in FIG. 1A, or FIG. 6A. The gap between the first end plate 110 and the second end plate 120 at the anterior “A” face of implants 100,600 is greater than at the posterior “P” face of implants 100,600. The greater gap at the anterior face vs. the posterior face of implants 100,600 results in the flexion (forward bending) movement being facilitated to a greater degree than extension (backward bending) movement. Thus, for these embodiments, an example of a forward bending movement of up to 10° can be achieved while a backward bending movement of 5° will be achieved. These embodiments show implants 100,600 inserted between two vertebrae with two first keels 114 extending from the first end plate 110, and two second keels 124 extending from the second end plate 120. The first and second keels 114,124 are about perpendicular to the sagittal plane of the spine, and support the articulation of the first end plate 110 relative to the second end plate 120, about the spacer 130.

The embodiments of implants 100, 600 can be made of medical grade titanium, stainless steel or cobalt chrome. Other materials that have appropriate structural strength and that are suitable for implantation into a patient can also be used.

One class of materials contemplated for use in implant 100 is the class of biocompatible polymers. Copolymers, blends and composites of polymers are also contemplated for fabrication of parts of the disclosed device. A copolymer is a polymer derived from more than one species of monomer. A polymer composite is a heterogeneous combination of two or more materials, wherein the constituents are not miscible, and therefore exhibit an interface between one another. A polymer blend is a macroscopically homogeneous mixture of two or more different species of polymer.

One group of biocompatible polymers are the polyaryl ester ketones which has several members, which include polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). PEEK has proven as a durable material for implants, as well as meeting criteria of biocompatibility. Medical grade PEEK is available from Victrex Corporation under the product name PEEK-OPTIMA. Medical grade PEKK is available from Oxford Performance Materials under the name OXPEKK, and also from CoorsTek under the name BioPEKK. Still another interesting group of biocompatible polymers are polyalkyl biocompatible polymers, such as polyethylenes, polypropylenes, and the like.

These medical grade biocompatible polymers are also available as reinforced polymer materials. To reinforce a polymeric material, fillers, are added to a polymer, copolymer, polymer blend, or polymer composite. Fillers are added to modify properties, such as mechanical, optical, and thermal properties. In this case, fillers, such as carbon fibers, are added to reinforce the polymers mechanically to enhance strength for certain uses, such as load bearing devices.

In addition to disclosure of embodiments of an intervertebral implant, tools for preparing and inserting an intervertebral implant are also disclosed. FIG. 7A through 7D show an embodiment of a tool for preparing vertebral bodies to receive implants 100,600, while FIG. 8A through FIG. 8D show an embodiment of a tool for inserting embodiments of the disclosed intervertebral implants 100,600.

FIG. 7A through FIG. 7C are the top view, the side view, and an end view of the cutting tool 700. The cutting tool 700 has a handle 710 at its proximal end for controlling the tool during operation. As will be appreciated by those of skill in the art, the handle 710 can be removable or affixed to the cutting end. The distal end 702 of the tool 700 is solid head has an upper surface 705, and a lower surface 706. The upper surface 705 has a first blade 712 mounted thereon, and the lower surface 706 has a second blade 714 mounted thereon. Preferably the first blade 712 is about centered with the upper surface 705, and the second blade 714 is about centered with the lower surface 706. The first and second blades 712,714 are oriented to cut a space in a first and second intervertebral body for the first and second keels 114,124 of implants 100,600. The space is perpendicular to the sagittal plane of the vertebrae, and allows for the lateral insertion of the implants 100,600. FIG. 7C is a view of the distal end of the cutting tool 700 showing the beveled end 716 and the first and second blades 712,714. The height h of the head 702 of the cutting tool 700 approximates the distance between two vertebral bodies or the height of the disk space. In this embodiment of cutting tool 700, the blades 712, 714 extend above and below the head 702.

As will be appreciated by those of skill in the art, the tool shown in FIG. 7A can be modified such that instead of cutting keel-receiving channels in the upper and lower vertebral bodies at the same time, two tools are provided so that only one vertebral body is cut for keel-receiving channels at a time. For example, an alternative embodiment of cutting tool 700 has a first tool with a single blade mounted on the head 702. A second tool could be provided having a single blade mounted on the head 702, and additionally on the opposing surface, a guide. The guide on the surface opposite the surface with the blade is designed to engage with the first keel receiving channel cut the first vertebrae with the first tool to ensure that the second cut is optimally aligned with the first cut.

FIG. 8A through FIG. 8D depict an embodiment of the implanting tool used to insert the implant 600 of FIG. 6A between vertebral bodies. FIG. 8A is a side view of the implantation tool 800 that has a handle 810 and an implant holder 820. The implant holder 820 has an implant conforming surface 824 and four pins 822 for holding the first end plate 610 and the second end plate 620 implant 600. The conforming surface 824 is curved to follow the convex outer LL edges of the first and second end plates 610, 620, respectively, for an implant inserted from the left lateral side of a patient. The implant 600 nests within a conforming surface 824 and is held by pins 822. FIG. 8C shows the distal view of the end of the tool with four pins 822 for securing the first and second end plate of the implant.

A variety of kits can be assembled that include an implant 100 (or 600) sized for a particular patient. The kit could also include several cutting tools 700 and several implanting tools 800 or a single handle that cooperates with cutting ends 702 and implantation ends 820.

FIG. 9 is a block diagram showing the basic steps of the method for laterally inserting the embodiments of implants 100,600. First the spine is exposed through a lateral access 910, then the intervertebral disk is removed laterally 920, if necessary. A tool, such as the one depicted in FIG. 7A is inserted laterally between the vertebral bodies to create channels in the bodies to receive the keels of the implant. The implant is then inserted laterally 930 between two vertebrae and the wound is closed 940. This procedure can be followed for either a left lateral approach or right lateral approach. For a left lateral approach, the teeth 115,125 of upper and lower keels 114, 124 would be pointed towards the left lateral face of the device in order to aid in retaining embodiments of implants 100,600 in place. For a right lateral approach, the teeth would point towards the right lateral face of the device.

What has been disclosed herein has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit what is disclosed to the precise forms described. Many modifications and variations will be apparent to the practitioner skilled in the art. What is disclosed was chosen and described in order to best explain the principles and practical application of the embodiments described herein, thereby enabling others skilled in the art to understand the various embodiments and various modifications that are suited to the particular use contemplated. It is intended that the scope of what is disclosed be defined by the following claims and their equivalence. 

1. An intervertebral implant comprising: a first end plate with a first inner surface; a second end plate with a second inner surface opposing the first inner surface, where the second inner surface has an articulating element formed thereon; and an attachment mechanism adapted to engage a vertebral body, wherein the attachment mechanism is adapted to extend, when implanted, along a lateral direction with respect to the vertebral body.
 2. The implant of claim 1 wherein the articulating element allows movement of the vertebral body in between flexion to extension directions.
 3. The implant of claim 1 wherein the attachment mechanism is aligned with and supports the articulating element.
 4. The implant of claim 1 wherein the articulating element further comprises an elongated hemi-cylindrical structure protruding from the second inner surface and an elongated cavity in the first inner surface adapted to receive the hemi-cylindrical structure.
 5. The implant of claim 1 wherein the attachment mechanism is a keel upstanding from at least one of the first end plate and the second end plate.
 6. An intervertebral implant comprising: a first end plate adapted to mate with a first vertebral body further comprising: a first inner surface; a first outer surface; and at least one keel on the first outer surface, wherein the keel is adapted to be perpendicular to a sagittal plane of the first vertebral body when implanted thereto; a second end plate adapted to mate with a second vertebral body further comprising; a second inner surface opposing the first inner surface, wherein the second inner surface has a spacer coupled thereto; and a second outer surface.
 7. The implant of claim 6 wherein the spacer allows bending from flexion to extension.
 8. The implant of claim 6, where the keel is aligned with and supports the spacer.
 9. The implant of claim 6, further comprising at least one keel on the second outer surface, wherein the keel is oriented perpendicular to the sagittal plane when implanted to a second vertebral body.
 10. The implant of claim 9 wherein the keel is supports the spacer.
 11. An intervertebral implant comprising: a first end plate adapted to mate with a first vertebral body further comprising: a first inner surface; a first outer surface; and at least one keel on the first outer surface, where the keel is adapted to be perpendicular to the sagittal plane of the vertebrae when implanted thereto; a second end plate adapted to mate a second vertebrae, comprising: a second inner surface opposing the first inner surface, where the second inner surface has extending spacer therefrom; a second outer surface; and at least one keel on the second outer surface, where the keel is adapted to be perpendicular to the sagittal plane of the vertebral body when implanted thereto.
 12. The intervertebral implant of claim 11 wherein the spacer allows bending from flexion to extension.
 13. The intervertebral implant of claim 11 wherein the keels on the first outer surface and the second outer surface support the spacer.
 14. The intervertebral implant of claim 11 wherein the first end plate and second end plate have a lateral dimension longer than an anterior-posterior dimension.
 15. An interspinous disk replacement implant adatped to be inserted between adjacent vertebral bodies, the implant having a first end plate, a second end plate, and an articulating element formed on the second end plate, the improvement comprising the implant having at least one keel that is about perpendicular to the sagittal plane of a vertebral body.
 16. The implant of claim 15 wherein the articulating element is hemi-cylindrical.
 17. An interspinous disk replacement implant adapted to be inserted between adjacent vertebral bodies, the implant having an articulating unit with a first end plate having a first inner surface with a first socket therein, a second end plate having a second inner surface opposing the first inner surface, the second inner surface with an articulating element formed thereon, where the articulating element is at least partially received in the first socket, the improvement of the implant comprising the implant having at least one keel extending from the articulating unit that is about perpendicular to the sagittal plane of a vertebral body.
 18. The implant of claim 17 wherein the articulating element is hemi-cylindrical.
 19. An interspinous disk replacement implant having a first end plate, a second end plate, and an articulating element between formed on the second end plate, the improvement comprising the implant having an attachment mechanism that supports the articulating element, the attachment mechanism adapted to laterally engage an adjacent vertebrae.
 20. The implant of claim 19 wherein the attachment mechanism is at least one keel.
 21. The implant of claim 19 wherein the articulating element is hemi-cylindrical.
 22. An interspinous disk replacement implant having an articulating unit with a first end plate having a first inner surface with a first socket therein, a second end plate having a second inner surface opposing the first inner surface, the second inner surface with an articulating element formed thereon, where the articulating element is at least partially received in the first socket, the improvement of the implant comprising the implant having an attachment mechanism is aligned with and supports the articulating element, the attachment mechanism adapted to laterally engage an adjacent vertebrae.
 23. The implant of claim 22 wherein the attachment mechanism is at least one keel.
 24. The implant of claim 22 wherein the articulating element is hemi-cylindrical.
 25. A kit to insert an interspinous disk replacement implant in a spine, the kit comprising: an interspinous disk replacement implant adapted for lateral insertion into the spine; and at least one tool for preparing the spine to receive the implant.
 26. An interspinious implant comprising: a first end plate having a first anterior end, a first posterior end and two first lateral ends extending between the first anterior and posterior ends; a second end plate having a second anterior end, a second posterior end and two second lateral ends extending between the second anterior and posterior ends; a spacer extending from the second end plate, the spacer having an elongated hemi-cylindrical configuration; a first keel protruding from a first outer surface of the first end plate, wherein the first keel is oriented lengthwise between the two first lateral ends; and a second keel protruding from a second outer surface of the second end plate, wherein the second keel is oriented lengthweise between the two second lateral ends.
 27. An interspinous implant adapted to be inserted between adjacent vertebral bodies comprising: an implant body having a first outer surface adapted to mate with a first vertebral body and a second outer surface adapted to mate with a second vertebral body; an articulating element within the implant body, the articulating element having an elongated spacer and corresponding elongated socket; a first keel protruding from the first outer surface and oriented generally parallel to the articulating element. 